Combination highway and rail vehicles are in general use and usually include a main frame having front steerable wheels and rear traction wheels for highway travel and, additionally, forwardly and rearwardly carried rail wheels for rail travel. In highway travel, the rail wheels are supported in a ground clearance relation, and in rail travel the rail wheels guide the travel of the vehicle on the rails with the vehicle road wheels ridable on the rails. During rail travel, the rail wheels support a part of the vehicle weight. However, in road travel the full weight of the vehicle is carried on the front and rear vehicle axles.
The equipment provided on these combination highway and rail vehicles varies according to the specifications for the different rail jobs to be performed. Weight or load limits on the vehicle axles for rail travel are not critical. However, in converting the vehicle from rail to highway travel, the load from the rail wheel axles transferred to the vehicle highway axles often exceeds the safe legal load limits for the vehicle axles. Unless special permits for such axle overloading for road travel are obtained, fines and other penalties may be incurred by the vehicle owner.
This objection is overcome by the present invention by mounting spare road wheels on the tag or rear rail wheel assembly and then utilizing the tag assembly to support a portion of the vehicle weight so that the gross vehicle load is distributed on the vehicle axles within legal load limits for highway travel.